Light transmittance control film and composition for the light transmittance control film

ABSTRACT

Provided are a composition for a light transmittance control film, and a light transmittance control film. According to the inventive concept, the light transmittance control film includes a matrix part including a copolymer and a polymer chain which is grafted to the copolymer; and a dispersed part including a polymer derived from a first monomer, and are provided in the matrix part, wherein the polymer chain is derived from the first monomer, first light transmittance is shown while external force is applied, and second light transmittance which is greater than the first light transmittance may be shown after the external force is removed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. non-provisional patent application is a continuation of U.S.application Ser. No. 17/324,869, filed May 19, 2021, which is acontinuation of U.S. application Ser. No. 16/306,866, filed Dec. 3,2018, now U.S. Pat. No. 11,041,055, which is a U.S. National Phase ofInternational Application No. PCT/KR2018/004576, filed Apr. 19, 2018,which claims priority under 35 U.S.C. § 119 of Korean Patent ApplicationNos. 10-2017-0051197, filed on Apr. 20, 2017 and 10-2018-0002435, filedon Jan. 8, 2018, the entire contents of which are hereby incorporated byreference.

TECHNICAL FIELD

The present invention disclosed herein relates to a light transmittancecontrol film and a composition for the light transmittance control film.

BACKGROUND ART

The present invention discloses a light transmission control film notcontaining any liquid crystal or electrochromic molecules, whichimproves the defects of a film type light transmission control modulebased on liquid crystal and electrochromic molecules.

A method for controlling light intensity using low molecular weightliquid crystals (LCs) uses polarized light based on operation principle,and thus has drawbacks of the increase in power consumption due to lightloss and the use of components such as a polarizing plate and anexpensive liquid crystal material. A method for controlling lightintensity using polymer-dispersed liquid crystals (PDLCs) has a drawbackof low shielding ratio of light because of light scattering under noelectric field. A light absorption control method via the oxidation andreduction of an electrochromic material and the alignment of a dichromicdye and a particle which is dispersed and suspended, respectively, in apolymer has drawbacks of high manufacturing cost from the materials andpackaging and low transmittance change of about 30-50% due to thelimitation of light control mechanism.

DISCLOSURE OF THE INVENTION Technical Problem

The present invention is to provide a film which may simply controllight transmittance without an electrical filed, and a composition for alight transmittance control film for preparing the same.

The present invention is not limited to the above-mentioned task, andunmentioned tasks will be apparently understood by the description belowfor a person skilled in the art.

Technical Solution

The present invention relates to a light transmittance control film anda composition for the light transmittance control film. According to thepresent invention, a light transmittance control film includes a matrixpart including a copolymer and a polymer chain which is combined withthe copolymer; and a dispersed part including a polymer derived from afirst monomer, which is provided in the matrix part, wherein the polymerchain may be derived from the first monomer. First light transmittancemay be shown while external force is applied, and second lighttransmittance which is greater than the first light transmittance may beshown after the external force is removed.

In some embodiments, the second light transmittance may be about 35% toabout 95% with respect to visible light.

In some embodiments, numerous voids may be provided between thedispersed part and the matrix part while the external force is applied,and the voids may be disappeared after the external force is removed.

In some embodiments, the dispersed part may have a greater initialmodulus than the matrix part.

In some embodiments, the dispersed part may have about 100 to about100,000 times as much initial modulus as the matrix part has.

In some embodiments, a difference between a refractive index of thematrix part and a refractive index of the dispersed part may be lessthan about 5%.

In some embodiments, the external force may include tensile force.

In some embodiments, the first monomer may be represented by thefollowing Formula 1:

In Formula 1, A1 and A2 are each independently a single bond, oxygen(O), —NH—, or sulfur (S), R1 is hydrogen, halogen, linear or branchedalkyl group of 1 to 8 carbon atoms, or halogen-substituted linear orbranched alkyl group of 1 to 8 carbon atoms, and R2, R3, and R4 are eachindependently hydrogen, halogen, or linear or branched alkyl group of 1to 5 carbon atoms.

In some embodiments, the matrix part may be represented by the followingFormula 6A:

In Formula 6A, R11 is represented by the following Formula 2B, R12, R13,and R14 are each independently hydrogen, halogen, linear or branchedalkyl group of 1 to 5 carbon atoms, or substituted or unsubstitutedphenyl group of 6 to 13 carbon atoms, R15 may include at least one ofthe materials represented by the following Formula 6B, and R16 mayinclude at least one material represented by the following Formula 6C:

In Formula 2B, * means a bonded part of Formula 6A to Si, B is a singlebond, or linear or branched alkyl group of 1 to 5 carbon atoms,carbonyl, ester, acetate, amide, or —S—CO— group, and R21, R22, and R23are each independently hydrogen, halogen, or linear or branched alkylgroup of 1 to 5 carbon atoms:

In Formula 6B, * means a part bonded to Si in Formula 6A, A1 and A2 areeach independently a single bond, oxygen (O), —NH—, or sulfur (S), B isa single bond, linear or branched alkyl group of 1 to 5 carbon atoms,carbonyl, ester, acetate, amide, or —S—CO— group, R1 is hydrogen,halogen, linear or branched alkyl group of 1 to 8 carbon atoms, orhalogen-substituted linear or branched alkyl group of 1 to 8 carbonatoms, R2, R3, and R4 are each independently hydrogen, halogen, orlinear or branched alkyl group of 1 to 5 carbon atoms, R21, R22, and R23are each independently hydrogen, halogen, linear or branched alkyl groupof 1 to 5 carbon atoms, or substituted or unsubstituted phenyl group of6 to 13 carbon atoms, and m6 is an integer selected from 1 to 100:

In Formula 6C, * means a part bonded to Si in Formula 6A, A1 and A2 areeach independently a single bond, oxygen (O), —NH—, or sulfur (S), B isa single bond, linear or branched alkyl group of 1 to 5 carbon atoms,carbonyl, ester, acetate, amide, or —S—CO— group, R1 is hydrogen,halogen, linear or branched alkyl group of 1 to 8 carbon atoms, orhalogen-substituted linear or branched alkyl group of 1 to 8 carbonatoms, R2, R3, and R4 are each independently hydrogen, halogen, orlinear or branched alkyl group of 1 to 5 carbon atoms, R21, R22, and R23are each independently hydrogen, halogen, linear or branched alkyl groupof 1 to 5 carbon atoms, or substituted or unsubstituted phenyl group of6 to 13 carbon atoms, and m7 is an integer selected from 1 to 100.

According to the present invention, a composition for a lighttransmittance control film includes a first monomer; and a copolymerincluding a first polymer derived from a second monomer and a secondpolymer derived from a third monomer, wherein a molar ratio of the firstpolymer in the copolymer and the first monomer is from about 1:5 toabout 1:100, and a molar ratio of the first polymer and the secondpolymer in the copolymer is from about 1:4 to about 1:200.

In some embodiments, the first monomer may be represented by thefollowing Formula 1:

In Formula 1, A1 and A2 are each independently a single bond, oxygen(O), —NH—, or sulfur (S), R1 is hydrogen, halogen, linear or branchedalkyl group of 1 to 8 carbon atoms, or halogen-substituted linear orbranched alkyl group of 1 to 8 carbon atoms, and R2, R3, and R4 are eachindependently hydrogen, halogen, or linear or branched alkyl group of 1to 5 carbon atoms.

In some embodiments, the first polymer may include a polymerization unitrepresented by the following Formula 2A:

In Formula 2A, R11 is represented by the following Formula 2B, R12 ishydrogen, halogen, linear or branched alkyl group of 1 to 5 carbonatoms, or substituted or unsubstituted phenyl group of 6 to 13 carbonatoms, and m1 is an integer between 2 and 50:

In Formula 2B, B is a single bond, or linear or branched alkyl group of1 to 5 carbon atoms, carbonyl, ester, acetate, amide, or —S—CO— group,and R21, R22, and R23 are each independently hydrogen, halogen, orlinear or branched alkyl group of 1 to 5 carbon atoms.

In some embodiments, the second polymer may include a polymerizationunit represented by the following Formula 3:

In Formula 3, R13 and R14 are each independently hydrogen, halogen,linear or branched alkyl group of 1 to 5 carbon atoms, or substituted orunsubstituted phenyl group of 6 to 13 carbon atoms, and m2 is an integerbetween 10 and 10,000.

In some embodiments, the first monomer may include t-butyl acrylate, thecopolymer may include a silicon copolymer represented by the followingFormula 4B, where the silicon copolymer may have a weight averagemolecular weight of about 5,000 to about 500,000, and the siliconcopolymer may be dissolved in the t-butyl acrylate monomer:

In Formula 4B, a ratio of m1 and m2 is from about 1:4 to about 1:200.

In some embodiments, a molar ratio of the t-butyl acrylate monomer withrespect to a total molar ratio of a vinyl group included in thecopolymer may be from about 1:5 to about 1:100.

In some embodiments, a polymerization initiator may be further included.

In some embodiments, at least one of the first monomer and the copolymermay include a vinyl group, and the polymerization initiator may be about0.05-5 mol % based on the total of the vinyl group.

Advantageous Effects

According to the present invention, the light transmittance of theinvented film may be controlled by the intensity of the applied externalforce. The film is transparent before applying the external force. Thetransmittance of the light transmittance control film may decrease dueto a stress-whitening phenomenon. The light transmittance control filmmay have excellent elasticity recovery properties. After the externalforce is removed, the light transmittance control film may return to theinitial state before applying the external force. Accordingly, lighttransmittance may be easily controlled. The light transmittance controlfilm may be simply manufactured by the photopolymerization reaction of acomposition for a light transmittance control film.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further completeunderstanding of the present invention, and reference numbers are shownbelow.

FIG. 1 is a schematic diagram showing a molecular composition for alight transmittance control film according to embodiments of the presentinvention;

FIG. 2 is a plane view of schematic diagram showing a lighttransmittance control film according to embodiments;

FIG. 3 schematically shows a molecular chain composition of the lighttransmittance control film of FIG. 2 ;

FIG. 4 is a perspective view for explaining a manufacturing process of alight transmittance control film according to embodiments;

FIG. 5 is a diagram for explaining a method for controlling lighttransmittance using the light transmittance control film of FIG. 2 ;

FIG. 6 is a graph showing the light transmittance of ExperimentalExample F 1-20, Experimental Example F 1-30, Experimental Example F2-20, Experimental Example F 2-30, Experimental Example F 3-20, andExperimental Example F 3-30 films in accordance with wavelength;

FIG. 7 a is a result showing the light transmittance of ExperimentalExample F 3-20 film in accordance with tensile strain;

FIG. 7 b is an analysis result of the light transmittance ofExperimental Example F 2-20, Experimental Example F 3-20, andExperimental Example F 3-30 films in accordance with wavelength while atensile strain of 0.2 is applied to the light transmittance controlfilms;

FIG. 8 a is a scanning electron microscope (SEM) plain image ofExperimental Example F 2-20 film while a tensile strain of 0.2 isapplied to a light transmittance control film;

FIG. 8 b is a SEM plain image of Experimental Example F 2-20 film whilea tensile strain of 0.4 is applied to a light transmittance controlfilm;

FIG. 8 c is a SEM plain image of Experimental Example F 2-20 film whilea tensile strain of 0.8 is applied to a light transmittance controlfilm;

FIG. 9 is a graph showing analysis results of differential scanningcalorimetry (DSC) of Experimental Example F 1-20, Experimental Example F1-30, Experimental Example F 2-20, Experimental Example F 2-30,Experimental Example F 3-20, and Experimental Example F 3-30 films;

FIG. 10 a , FIG. 10 b , FIG. 10 c , and FIG. 10 d are transmissionelectron microscope (TEM) cross-sectional images of Experimental ExampleF 1-20, Experimental Example F 2-20, Experimental Example F 3-20, andExperimental Example F 3-30 films;

FIG. 11 a is a photo-image of Experimental Example F 3-20 film whiletensile force is not applied;

FIG. 11 b is a photo-image of Experimental Example F 3-20 film duringapplying tensile force; and

FIG. 11 c is a photo-image of Experimental Example F 3-20 film whentensile force is removed after applying the tensile force.

MODE FOR CARRYING OUT THE INVENTION

In order to sufficiently understand the configuration and effect of thepresent invention, preferred embodiments of the present invention willbe described with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstructed as limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the present inventionto those skilled in the art. A person skilled in the art couldunderstand that what circumstance is appropriate for conducting theconcept of the present invention.

The terminology used herein is for the purpose of describing exampleembodiments and is not intended to limit the present inventive concept.As used herein, the singular forms are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It willbe further understood that the terms “comprises” and/or “comprising,”when used in this disclosure, specify the presence of stated features,steps, operations, and/or devices, but do not preclude the presence oraddition of one or more other features, steps, operations, and/ordevices thereof.

It will also be understood that when a layer (or film) is referred to asbeing on another layer (or film) or substrate, it can be directly on theother layer (or film) or substrate, or a third intervening layer (orfilm) may also be present.

It will be understood that, although the terms first, second, third etc.may be used herein to describe various regions, layers (or films), etc.these regions and layers should not be limited by these terms. Theseterms are only used to distinguish one region or layer (or film) fromanother region or layer (film). Thus, a first layer discussed belowcould be termed a second layer. Example embodiments embodied anddescribed herein may include complementary example embodiments thereof.Like reference numerals refer to like elements throughout.

The terminology used in exemplary embodiments of the present inventionmay be interpreted as a meaning commonly known to a person skilled inthe art, unless otherwise defined.

A film composition according to the present invention will be explained.

FIG. 1 is a schematic diagram showing a molecular composition for alight transmittance control film according to embodiments of the presentinvention.

Referring to FIG. 1 , a composition (10) for a light transmittancecontrol film may include a first monomer (100) and a copolymer (200).The first monomer (100) may be represented by Formula 1 below.

In Formula 1, A1 and A2 may be each independently a single bond, oxygen(O), —NH—, or sulfur (S), R1 may be hydrogen, halogen, linear orbranched alkyl group of 1 to 8 carbon atoms, or halogen-substitutedlinear or branched alkyl group of 1 to 8 carbon atoms, and R2, R3, andR4 may be each independently hydrogen, halogen, or linear or branchedalkyl group of 1 to 5 carbon atoms.

According to an embodiment, the first monomer (100) may include anacryl-based monomer or a vinyl-based monomer. The first monomer (100)may include, for example, at least one selected from styrene,2,3,4,5,6-pentafluorostyrene, methylacrylate, methylmethacrylate, ethylacrylate, ethylmethacrylate, butylacrylate, butylmethacrylate,t-butylacrylate, t-butylmethacrylate, hexylacrylate, hexylmethacrylate,octylacrylate, octylmethacrylate, octadecylacrylate,octadecylmethacrylate, dodecylacrylate, dodecylmethacrylate, vinylacetate, trifluoroacetic acid allyl ester, trifluoroacetic acid vinylester, 2,2,2-trifluoroethyl methacrylate, acrylic acid1,1,1,3,3,3-hexafluoroisopropyl ester, methacrylic acid1,1,1,3,3,3-hexafluoroisopropyl ester, and1-pentafluorophenylpyrrole-2,5-dione.

The copolymer (200) may include a first polymer and a second polymer.The weight average molecular weight of the copolymer (200) may be fromabout 5,000 to about 500,000. The first polymer may include apolymerization unit derived from a second monomer. The first polymer mayinclude a polymerization unit represented by Formula 2A below.

In Formula 2A, R11 may be represented by Formula 2B below. R12 may behydrogen, halogen, linear or branched alkyl group of 1 to 5 carbonatoms, or substituted or unsubstituted phenyl group of 6 to 13 carbonatoms, and m1 may be an integer between 2 and 50.

In Formula 2B, B may be a single bond, or linear or branched alkyl groupof 1 to 5 carbon atoms, carbonyl, ester, acetate, amide, or —S—CO—group, and R21, R22, and R23 may be each independently hydrogen,halogen, or linear or branched alkyl group of 1 to 5 carbon atoms.

The first polymer may include a reactive group. The reactive group maybe a group represented by Formula 2B.

A second polymer may be combined with the first polymer. The secondpolymer may include a polymerization unit represented by Formula 3below. The second polymer may be derived from a third monomer. The thirdmonomer may be different from the first monomer (100) and the secondmonomer.

In Formula 3, R13 and R14 may be each independently hydrogen, halogen,linear or branched alkyl group of 1 to 5 carbon atoms, or substituted orunsubstituted phenyl group of 6 to 13 carbon atoms. m2 may be an integerbetween 10 and 10,000.

In the composition (10) for a light transmittance control film, themolar ratio of the total of the polymerization unit of the first polymerin the copolymer (200) to the first monomer (100) may be from about 1:5to about 1:100. Here, the total of the polymerization unit of the firstpolymer may be, for example, the total of m1 in Formula 2A.

According to an embodiment, the copolymer (200) may be represented bythe following Formula 4A:

In Formula 4A, R12, R13, and R14 may be each independently hydrogen,halogen, linear or branched alkyl group of 1 to 5 carbon atoms, orsubstituted or unsubstituted phenyl group of 6 to 13 carbon atoms, m1may be an integer between 2 and 50, m2 may be an integer between 10 and10,000, and m1:m2 may be from about 1:4 to about 1:200. R11 may berepresented by Formula 2B.

The copolymer (200) may be prepared by the polymerization reaction of asecond monomer and a third monomer as Reaction 1 below.

In Reaction 1, R11, R12, R13, R14, m1, and m2 are the same as defined inFormula 2A, Formula 2B, and Formula 4A.

The composition (10) for a light transmittance control film may furtherinclude a polymerization initiator (300). The polymerization initiator(300) may include a photopolymerization initiator. The polymerizationinitiator (300) may include, for example,2,2-dimethoxy-2-phenylacetophenone. In another embodiment, thepolymerization initiator (300) may include a thermal polymerizationinitiator.

According to an embodiment, the first monomer (100) may include t-butylacrylate, the copolymer (200) may include a silicon copolymerrepresented by Formula 4B below, and the silicon copolymer may have aweight average molecular weight of about 5,000 to about 500,000. Thesilicon copolymer may be dissolved in t-butyl acrylate.

In Formula 4B, the ratio of m1 and m2 is from about 1:4 to about 1:200.

The molar ratio of the t-butyl acrylate with respect to the total molarratio of the vinyl group included in the copolymer (200) may be fromabout 1:5 to about 1:100. At least one of the first monomer (100) andthe copolymer (200) may include a vinyl group. If the composition (10)for a light transmittance control film further includes thepolymerization initiator (300), the polymerization initiator (300) maybe from about 0.05 mol % to about 5 mol % with respect to the total ofthe vinyl group.

Generally, in a semicrystalline polymer such as polyethylene,polypropylene, polyoxymethylene, polyethyleneterephthalate, andpolyamide, it is known that voids with a size of several nanometers areformed in the process of growing a noncrystalline region from lamellaecrystals by extension, and the voids are grown to a size of several tensor several hundreds nanometers, which may arise light scattering byextension near break, thereby showing stress-whitening by stress atbreak. The stress-whitening is not shown by compression or torsionalstress. Alternatively, irrespective of the crystallinity of a polymer,if a composite film in which a binary polymer or inorganic materials aredispersed in a polymer matrix is extended, voids may be formed at theinterface between a polymer and a dispersant due to the difference oftensile strain (ε) between a polymer matrix and a dispersant, and suchvoids grow with continuous tension and visible light passing through afilm is scattered near break, thereby arising whitening phenomenon bywhich the film becomes opaque. Since, however, such phenomenon isgenerated when the polymer film nearly breaks the control of lighttransmittance by the stress-whitening is irreversible with respect tothe change of the tensile stress of the film. In addition, since thestress-whitening phenomenon is mainly generated in a semicrystallinepolymer or a polymer composite film in which a dispersant is, the lighttransmittance of an initial polymer film before applying tensile stressmay decrease due to the light scattering of the crystal region or thedispersant.

The light transmittance control film in the present invention uses thestress-whitening phenomenon of a polymer and is a film of which lighttransmittance is controlled according to the applied mechanical strainor stress.

Hereinafter, a light transmittance control film and a method ofmanufacturing thereof will be explained.

FIG. 2 is a plane view of schematic diagram showing a lighttransmittance control film according to embodiments. FIG. 3schematically shows a molecular chain composition of the lighttransmittance control film of FIG. 2 . Hereinafter, overlapping partswith the above description will be omitted.

Referring to FIG. 2 , a light transmittance control film (1000) mayinclude a dispersed part (P1) and a matrix part (P2). The control oflight transmittance using the light transmittance control film (1000)will be explained in more detail in FIG. 5 . The dispersed part (P1) maybe provided in the matrix part (P2). The dispersed part (P1) may have acircular or elliptical shape. The dispersed part (P1) may have maximumdiameters of about 10 nm to about 500 nm.

The matrix part (P2) may play the role of the matrix of the lighttransmittance control film (1000). The content and volume of the matrixpart (P2) may be smaller than the content and volume of the dispersedpart (P1). The matrix part (P2) may include a polymerization unitderived from a monomer different from the dispersed part (P1). Thematrix part (P2) may have compatibility with the dispersed part (P1).

The light transmittance control film (1000) may have initial modulus ofabout 50 MPa or less. The dispersed part (P1) of the light transmittancecontrol film (1000) may have greater initial modulus than the matrixpart (P2). The initial modulus of the dispersed part (P1) may be 100times or more, specifically, 100 times to 100000 times more than that ofthe matrix part (P2). The initial modulus of the matrix part (P2) may befrom about 0.01 MPa to about 1 MPa, and the initial modulus of thedispersed part (P1) may be about 100 MPa or more, specifically, fromabout 100 MPa to about 100,000 MPa. In the disclosure, the initialmodulus may mean initial modulus at room temperature, for example, about25° C. The matrix part (P2) may have a greater strain than the dispersedpart (P1) against the constant external force. The matrix part (P2) mayhave excellent elastic recovery properties.

The matrix part (P2) may have the same or similar refractive index asthe dispersed part (P1). For example, the difference between therefractive index of the matrix part (P2) and the refractive index of thedispersed part (P1) may be less than about 5%. If the refractive indexof the matrix part (P2) is excessively greater than the refractive indexof the dispersed part (P1) (for example, the difference of refractiveindex is about 5% or more), the light transmittance of the lighttransmittance control film (1000) may decrease. Hereinafter, thepreparation method of the dispersed part (P1) and the matrix part (P2)will be explained.

Referring to FIG. 2 and FIG. 3 , the dispersed part (P1) may includehomopolymers. The dispersed part (P1) may include a polymerization unitderived from the first monomer (100). The first monomer (100) may berepresented by Formula 1. Accordingly, the dispersed part (P1) mayinclude a polymer represented by the following Formula 5:

In Formula 5, A1 and A2 are each independently a single bond, oxygen(O), —NH—, or sulfur (S), R1 is hydrogen, halogen, linear or branchedalkyl group of 1 to 8 carbon atoms, or halogen-substituted linear orbranched alkyl group of 1 to 8 carbon atoms, and R2, R3, and R4 are eachindependently hydrogen, halogen, or linear or branched alkyl group of 1to 5 carbon atoms. n is an integer between 2 and 5000.

In another embodiment, the dispersed part (P1) may include inorganicmaterials.

The matrix part (P2) may include a copolymer (200) and a polymer chain(110). The copolymer (200) may be random, alternative, or block types.The copolymer (200) may play the role of a main chain. The copolymer(200) may include a first polymer and a second polymer as described inFIG. 1 . The second polymer may be represented by Formula 3. Aftercuring the composition for the light transmittance control film (10) ofFIG. 1 , the polymer chain (110) may be formed and grafted into thecopolymer (200). After curing the composition for the lighttransmittance control film (10), the polymer chain (110) may be bondedto the first polymer. The polymer chain (110) may include polymerizationunits derived from the first monomer (100). After the composition (10)for the light transmittance control film is cured, the matrix part (P2)may be represented by Formula 6A below. In this case, the matrix part(P2) may have a weight average molecular weight of about 5,000-500,000.

In Formula 6A, R11 may be represented by Formula 2B, R12, R13, and R14may be each independently hydrogen, halogen, linear or branched alkylgroup of 1 to 5 carbon atoms, or substituted or unsubstituted phenylgroup of 6 to 13 carbon atoms. The sum of m3, m4, and m5 may be the sameas m1 of Formula 4A. R15 may be represented by Formula 6B below. R16 maybe represented by Formula 6C below.

In Formula 6B, * may mean a part bonded to Si in Formula 6A, A1 and A2may be each independently a single bond, oxygen (O), —NH—, or sulfur(S), B may be a single bond, linear or branched alkyl group of 1 to 5carbon atoms, carbonyl, ester, acetate, amide, or —S—CO— group, R1 maybe hydrogen, halogen, linear or branched alkyl group of 1 to 8 carbonatoms, or halogen-substituted linear or branched alkyl group of 1 to 8carbon atoms, R2, R3, and R4 may be each independently hydrogen,halogen, or linear or branched alkyl group of 1 to 5 carbon atoms, R21,R22, and R23 may be each independently hydrogen, halogen, linear orbranched alkyl group of 1 to 5 carbon atoms, or substituted orunsubstituted phenyl of 6 to 13 carbon atoms. m6 may be an integerselected from 1 to 100.

In Formula 6C, * means a part bonded to Si in Formula 6A, A1 and A2 areeach independently a single bond, oxygen (O), —NH—, or sulfur (S), B isa single bond, linear or branched alkyl group of 1 to 5 carbon atoms,carbonyl, ester, acetate, amide, or —S—CO— group, R1 is hydrogen,halogen, linear or branched alkyl group of 1 to 8 carbon atoms, orhalogen-substituted linear or branched alkyl group of 1 to 8 carbonatoms, R2, R3, and R4 are each independently hydrogen, halogen, orlinear or branched alkyl group of 1 to 5 carbon atoms, R21, R22, and R23are each independently hydrogen, halogen, linear or branched alkyl groupof 1 to 5 carbon atoms, or substituted or unsubstituted phenyl group of6 to 13 carbon atoms, and m7 is an integer selected from 1 to 100.

Referring to FIG. 1 and FIG. 3 , the light transmittance control film(1000) may be manufactured using the composition (10) for the lighttransmittance control film as explained in FIG. 1 . For example, by thepolymerization reaction of the composition (10) for the lighttransmittance control film, dispersed part (P1) and a matrix part (P2)may be formed. The polymerization reaction of the composition (10) forthe light transmittance control film may be initiated by light or heat.The manufacture of the light transmittance control film (1000) mayinclude forming the dispersed part (P1) by the polymerization reactionof the first monomer (100) and performing graft polymerization orcrosslinking reaction of the first monomer (100) into the copolymer(200). The polymerization reaction of the first monomer (100) and thecopolymer (200) may be performed by graft polymerization reaction. Inthis case, the vinyl group of the first polymer may function as areactive group so as to be bonded to the polymer chain (110).

The composition (10) for the light transmittance control film mayinclude a plurality of copolymers (200). During the polymerizationreaction, the copolymers (200) may be directly crosslinked from eachother, or connected via at least one of the polymer chains (110).Accordingly, the matrix part (P2) shown in FIG. 3 may be formed. Inanother embodiment, the matrix part (P2) may further include fourthpolymerization units derived from the fourth monomer. In this case, thefourth monomer may be different from the first to third monomers.

The polymer chains (110) of the matrix part (P2) may be derived from thesame monomer as the dispersed part (P1), for example, the first monomer(100). Accordingly, the matrix part (P2) may have compatibility with thedispersed part (P1). For example, though the copolymer (200) has lowercompatibility with the dispersed part (P1), the matrix part (P2) mayhave excellent compatibility with the dispersed part (P1) by controllingthe amount of the grafted polymer (110) in the matrix part (P2).

By controlling the molar ratio between the reactive groups of thecopolymer (200) and the first monomer (100) in the composition (10) forthe light transmittance control film, the amount of the grafted polymer(110) and the dispersed part (P1) of the light transmittance controlfilm (1000) may be controlled. The reactive group of the copolymer (200)may be a reactive group included in the first polymer of the copolymer(200). Accordingly, the amount of the dispersed part (P1) in the lighttransmittance control film (1000) and the size of dispersed particlesmay be controlled. In the present disclosure, the size may mean themaximum diameter unless otherwise explained.

According to exemplary embodiments, the amount of the polymer (110) inthe matrix part (P2) is controlled, and the light transmittance of thelight transmittance control film (1000) may be controlled beforeapplying external force. For example, even though the difference of therefractive index of the copolymer (200) and the refractive index of thedispersed part (P1) in FIG. 3 is greater than about 5%, compatibility ofthe matrix part (P2) and the dispersed part (P1) increases as thepolymer chains (110) are bonded to the copolymer (200), and the size ofdispersed particles may decrease, light scattering degree may decrease,and the light transmittance of the light transmittance control film(1000) may increase. If the refractive index of the matrix part (P2)approaches the refractive index of the dispersed part (P1), the lighttransmittance of the light transmittance control film (1000) mayincrease.

FIG. 4 is a perspective view for explaining a manufacturing process of alight transmittance control film according to embodiments. Hereinafter,overlapping parts with the above explanation will be omitted.

Referring to FIG. 4 , a first substrate (510), a second substrate (520),a first spacer (530), and a second spacer (540) may be prepared. Thesecond substrate (520) may be separately disposed from the firstsubstrate (510) in a vertical direction. The first substrate (510) andthe second substrate (520) may be glass substrates. The first spacer(530) and the second spacer (540) may be disposed between the firstsubstrate (510) and the second substrate (520). The second spacer (540)may be separately disposed from the first spacer (530) in a horizontaldirection. The first spacer (530) and the second spacer (540) mayinclude organic materials such as polyimide. A room (550) may beprovided between the first substrate (510) and the second substrate(520), and the first spacer (530) and the second spacer (540).

A composition (10 in FIG. 1 ) for a light transmittance control film maybe supplied on the first substrate (510). The room (550) may be filledwith the composition (10) for a light transmittance control film. Forexample, the composition (10) for a light transmitting control film mayinclude a first monomer (100), a copolymer (200), and an initiator(300).

Ultraviolet (UV) light may be supplied onto the second substrate (520).By conducting UV irradiation, homopolymerization of the first monomer(100), and graft polymerization or crosslinking reaction between thefirst monomer (100) and the copolymer (200) in the composition (10) fora light transmittance control film may be performed. The polymerizationreaction of the composition (10) for a light transmittance control filmmay be the same as explained above. The composition (10) for a lighttransmittance control film may be UV-cured. Accordingly, the lighttransmittance control film (1000) explained in FIG. 2 and FIG. 3 may bemanufactured.

A method for controlling light transmittance using a light transmittancecontrol film will be explained.

FIG. 5 is a diagram for explaining a method for controlling lighttransmittance using the light transmittance control film of FIG. 2 .Hereinafter, the overlapping part with the above explanation will beomitted.

Referring to FIG. 2 , a light transmittance control film (1000) may be astate that external force (for example, tensile force) is not applied.In this case, the light transmittance control film (1000) may betransparent. For example, the transmittance of the light transmittancecontrol film (1000) in a visible region may be from about 35% to about95%. The visible light may mean light having a wavelength of about 400nm to about 700 nm. A matrix part (P2) may have compatibility with adispersed part (P1). Between the dispersed part (P1) and the matrix part(P2), voids may not be provided. In another embodiment, if voids areprovided between the dispersed part (P1) and the matrix part (P2), thevoids may be very small. The matrix part (P2) may have the same orsimilar refractive index as the dispersed part (P1). If the refractiveindex of the matrix part (P2) and the refractive index of the dispersedpart (P1) are quite different, or if compatibility between the dispersedpart (P1) and the matrix part (P2) is very low, the light transmittanceof the light transmittance control film (1000) may decrease. Accordingto exemplary embodiments, the difference between the refractive index ofthe matrix part (P2) and the refractive index of the dispersed part (P1)may be less than about 5%. If the dispersed part (P1) or the matrix part(P1) shows crystallinity, the light transmittance of the lighttransmittance control film (1000) may decrease. According to exemplaryembodiments, the dispersed part (P1) and the matrix part (P1) may beamorphous.

Referring to FIG. 5 , external force may be applied to the lighttransmittance control film (1000). The external force may be tensileforce. The external force may have a certain intensity value or more.The light transmittance of the light transmittance control film (1000)may decrease due to stress-whitening phenomenon when the external forceis applied. The matrix part (P2) may have a relatively small initialmodulus and may be elongated by the external force. In FIG. 5 , a brokenline indicates the matrix part (P2) before the application of tensileforce. The initial modulus of the matrix part (P2) may be, for example,from about 0.01 MPa to about 1 MPa. The dispersed part (P1) hasrelatively large initial modulus, and may be much less elongated thanthe matrix part (P2) when the external force is applied. For example,the initial modulus of the dispersed part (P1) may be about 100 MPa ormore, specifically, about 100 MPa to about 100,000 MPa. In anotherembodiment, the strain of the dispersed part (P1) may be very small whencompared to that of the matrix part (P2). Accordingly, voids (400) maybe formed between the dispersed part (P1) and the matrix part (P2). Inanother embodiment, while the tensile force is applied, the voids (400)may have a greater volume than the voids (not shown) while tensile forceis not applied. The voids (400) may be a vacuum state, or air may besupplied in the voids (400). The dispersed part (P1) and the matrix part(P2) may have a large difference of refractive index from that of thevoids (400). Due to the difference of refractive index, light passingthrough the elongated film may be scattered or reflected. Accordingly,the light transmittance of the light transmittance control film (1000)may decrease. In an embodiment, the light transmittance control film(1000) may become opaque.

As explained above, the dispersed part (P1) may have particles of about10 nm to about 500 nm in maximum diameter. If the maximum diameter ofparticles in the dispersed part (P1) is less than about 10 nm, thevolume of voids (400) occurring between the dispersed part (P1) and thematrix part (P2) may decrease. Accordingly, even though tensile force isapplied to the light transmittance control film (1000), the lighttransmittance change of the light transmittance control film (1000) maynot be large. For example, the light transmittance control film (1000)may become transparent. In this case, it may be hard to control thelight transmittance by the light transmittance control film (1000). Ifthe maximum diameter of particles in the dispersed part (P1) is greaterthan about 500 nm, the light transmittance control film (1000) maybecome opaque due to the dispersed particles themselves. Accordingly,even tensile force is applied to the light transmittance control film(1000), the light transmittance change of the light transmittancecontrol film (1000) may not be large. In this case, the control of thelight transmittance of the light transmittance control film (1000) maybecome difficult.

Referring to FIG. 2 again, the external force applied to the lighttransmittance control film (1000) may be removed. Since the matrix part(P2) has excellent elasticity recovery properties, it may return to theinitial state before applying the external force. For example, theinitial length of the matrix part (P2) may be recovered without anydeformation as explained in FIG. 5 . The voids (400) between thedispersed part (P1) and the matrix part (P2) may disappear. Accordingly,the light transmittance control film (1000) may be transparent again.For example, the light transmittance control film (1000) may havetransmittance of about 35% to about 95% in a visible region. Accordingto exemplary embodiment, the intensity of light penetrating to the lighttransmittance control film (1000) may be controlled according to theintensity of external force applied to the light transmittance controlfilm (1000). That is, the stress-whitening phenomenon of the lighttransmittance control film (1000) is reversibly controlled, and lighttransmittance may be controlled reversibly. The light transmittancecontrol film (1000) may be simply manufactured by thephoto-polymerization reaction of the composition (10) for a lighttransmittance control film. If the light transmittance control film(1000) is used in a LCD (Liquid Crystal Display) module, a polarizedfilm in the display module may be omitted. In this case, the displaymodule may be miniaturized. If the light transmittance control film(1000) is used as a window, it may be applied to a smart window withwhich external or inner view is controlled.

Hereinafter, the preparation of a composition and a film will beexplained referring to experimental examples of the present invention.

Preparation of Compositions

1-1. Preparation of Copolymer (Experimental Example PDMS 1)

After 70.08 g (473 mmol) of diethoxydimethylsilane and 2.35 g (14.7mmol) of diethoxymethylvinylsilane (feeding mole ratio=97.0:3.0) wereadded to a 250 ml of three-necked flask at room temperature (about 25°C.) under nitrogen, 7.6 ml of distilled water and 1.9 ml of hydrochloricacid (37%) were slowly added as polymerization catalysts to the flask.Then, the reaction temperature was elevated to about 70° C. Afterpolymerization reaction was performed for about 24 hours under anitrogen flow of 70 ml/min, the temperature was decreased to roomtemperature. The highly viscous copolymer was dissolved in 200 ml ofethyl acetate (EA) for dilution and then the polymer solution in EA waspoured into 700 ml of water to remove the catalysts. After the polymersolution layer was separated from the water layer for one day, theremaining water was removed from the polymer solution in EA usingmagnesium sulfate. After the magnesium sulfate was filtered off and EAwas removed by a vacuum evaporator at room temperature, the transparent,colorless, and highly viscous polymer was dried at 35° C. under vacuumfor two days for obtaining Experimental Example PDMS 1.

Identification of Experimental Example PDMS 1(poly(dimethylsiloxane-co-methylvinylsiloxane))

For identification of Experimental Example PDMS 1, gel permeationchromatography (GPC), Fourier transform infrared spectroscopy (IR), andproton nuclear magnetic resonance spectroscopy (′H NMR) were performed,and the yield was calculated.

The gel permeation chromatography was performed by using a Waters 2690Alliance gel permeation chromatograph equipped with a refractive indexdetector and tetrahydrofuran (THF) as a mobile phase at a flow rate of0.6 ml/min. The IR spectroscopy was performed by using a Nicolet 6700FT-IR spectrometer. The proton nuclear magnetic resonance spectroscopywas performed by using a Bruker 500 MHz NMR spectrometer andchloroform-d₁ (CDCl₃) was used as a solvent.

Yield: 33.0 g (91%);

GPC (THF, polystyrene standard): M_(n)=105,832; PD=1.61.

IR ν_(max) (Liquid, NaCl)/cm⁻¹: 3055w (═C—H str., vinyl); 2963s (C—Hstr., methyl); 1598w (C═C str., vinyl); 1411m (C—H benzene, methyl);1097s (Si—O str., siloxane). ¹H NMR δ_(H) (CDCl₃, 500 MHz): 5.92-6.04(2H, m, vinyl); 5.77-5.82 (H, m, vinyl); 0.07-0.10 (9H, m, methyl)

In order to measure the molecular weight and the molecular weightdistribution of Experimental Example PDMS 1, GPC analysis was performed.The number average molecular weight of Experimental Example PDMS 1 wasabout 10.6×10⁴ g/mol, and the weight average molecular weight thereofwas about 17.1×10⁴ g/mol. Polydispersivity of PDMS 1 was 1.61.

From the ¹H NMR analysis result of Experimental Example PDMS 1, eachpeak was observed at 0.1 ppm, 5.8 ppm, and 6.0 ppm. The peak around 0.1ppm corresponds to the hydrogen of Si—CH₃, the peak around 5.8 ppmcorresponds to the CH hydrogen of —CH═CH₂, and the peak around 5.9-6.0ppm corresponds to CH₂ hydrogen of —CH═CH₂. If the amount of hydrogen ineach environment was quantified considering each integral value of therelated peaks, the ratios of a polymerization unit includingdimethylsiloxane (m2 in Formula 2A) and a polymerization unit includingmethylvinylsiloxane (m1 in Formula 2A) in Experimental Example PDMS 1are about 0.97 and 0.03, respectively. From the result, the molar ratioof the polymerization units of the copolymer of Experimental ExamplePDMS 1 was nearly equal to the feeding mole ratio of the monomers. Fromthe results, it was found that Experimental Example PDMS 1 includedpoly(dimethylsiloxane-co-methylvinylsiloxane.

1-2. Preparation of Copolymer (Experimental Example PDMS 2)

A copolymer was prepared by performing the same method as ExperimentalExample PDMS 1 above. However, 80.01 g (540 mmol) ofdiethoxydimethylsilane and 5.55 g (34.6 mmol) ofdiethoxymethylvinylsilane (feeding mole ratio=94.0:6.0) were used asstarting materials. 8.9 ml of distilled water and 2.3 ml of hydrochloricacid (37%) were added as polymerization catalysts.

Identification of Experimental Example PDMS 2(poly(dimethylsiloxane-co-methylvinylsiloxane)

The calculation of yield, gel permeation chromatography (GPC) analysis,Fourier transform infrared spectroscopy spectrum analysis, and protonnuclear magnetic resonance spectroscopy (′H NMR) were performed by thesame method as PDMS 2.

Yield: 39.9 g (93%)

GPC (THF, polystyrene standard): Mn=108,379; PD=1.42

IR ν_(max) (Liquid, NaCl)/cm⁻¹: 3055w (═C—H str., vinyl); 2963s (C—Hstr., methyl); 1598w (C═C str., vinyl); 1410m (C—H benzene, methyl);1093s (Si—O str., siloxane). ¹H NMR δ_(H) (CDCl₃, 500 MHz): 5.92-6.04(2H, m, vinyl); 5.78-5.83 (H, m, vinyl); 0.08-0.11 (9H, m, methyl)

From the GPC analysis result of Experimental Example PDMS 2, the numberaverage molecular weight of Experimental Example PDMS 2 was about10.8×10⁴ g/mol, the weight average molecular weight thereof was about15.4×10⁴ g/mol, and the polydispersivity thereof was 1.42.

From 1H NMR analysis result of Experimental Example PDMS 2, each peakwas observed at 0.1 ppm, 5.8 ppm, and 5.9 ppm to 6.0 ppm. The peakaround 0.1 ppm corresponds to the hydrogen of Si—CH₃, the peak around5.8 ppm corresponds to CH hydrogen of —CH═CH₂ and the peak around 5.9ppm to 6.0 ppm corresponds to CH₂ hydrogen of —CH═CH₂.

From the result, Experimental Example PDMS 2 was found to includepoly(dimethylsiloxane-co-methylvinylsiloxane). Considering each integralvalue of the peaks, the ratios of a polymerization unit includingdimethylsiloxane (m2 in Formula 2A) and a polymerization unit includingmethylvinylsiloxane (m1 in Formula 2A) in Experimental Example PDMS 2were about 0.94 and 0.06, respectively. From the result, the molar ratioof the polymer units of the copolymer of Experimental Example PDMS 2 wasnearly equal to the feeding mole ratio of monomers.

1-3. Preparation of Copolymer (Experimental Example PDMS 3)

A copolymer was prepared by performing the same method as ExperimentalExample PDMS 1 above. However, 75.01 g (506 mmol) ofdiethoxydimethylsilane and 11.07 g (69.1 mmol) ofdiethoxymethylvinylsilane (feeding mole ratio=88:12) were used asstarting materials. 8.8 ml of distilled water and 2.3 ml of hydrochloricacid (37%) were added as polymerization catalysts.

Identification of Experimental Example PDMS 3(poly(dimethylsiloxane-co-methylvinylsiloxane)

The calculation of yield, gel permeation chromatography (GPC), Fouriertransform infrared spectroscopy spectrum (IR), and proton nuclearmagnetic resonance spectroscopy analysis (′H NMR) were performed forExperimental Example PDMS 3.

Yield: 40.2 g (93%); GPC (THF, polystyrene standard): M_(n)=88,113;PD=1.60.

IR ν_(max) (Liquid, NaCl)/cm⁻¹: 3055w (═C—H str., vinyl); 2963s (C—Hstr., methyl); 1598w (C═C str., vinyl); 1409m (C—H benzene, methyl);1093s (Si—O str., siloxane). ¹H NMR δ_(H) (CDCl₃, 500 MHz): 5.92-6.04(2H, m, vinyl); 5.78-5.85 (H, m, vinyl); 0.08-0.11 (9H, m, methyl).

From the analysis result of Experimental Example PDMS 3, the numberaverage molecular weight of Experimental Example PDMS 3 was about8.8×10⁴ g/mol, the weight average molecular weight thereof was about14.1×10⁴ g/mol, and the polydispersivity thereof was 1.60.

From the result, Experimental Example PDMS 3 was found to includepoly(dimethylsiloxane-co-methylvinylsiloxane). Considering each integralvalue of the peaks, the ratios of a polymerization unit includingdimethylsiloxane (m2 in Formula 2A) and a polymerization unit includingmethylvinylsiloxane (m1 in Formula 2A) in Experimental Example PDMS 3were about 0.88 and 0.12, respectively. From the result, the molar ratioof the polymer units of the copolymer of Experimental Example PDMS 3 wasnearly equal to the feeding mole ratio of monomers.

2-1. Preparation of Composition for Light Transmittance Control FilmAccording to Copolymers

Each of the copolymers prepared as explained above and t-butyl acrylate(first monomer) were mixed as in Table 1 below to prepare a composition.

To the composition, a polymerization initiator (photoinitiator) wasadded. 2,2-dimethoxy-2-phenylacetophenone was used as a polymerizationinitiator, and about 0.5 mol % of 2,2-dimethoxy-2-phenylacetophenone wasadded with respect to the equivalent of a vinyl group in a mixturesolution.

TABLE 1 Weight percent Mass of Mass of Mass of Mass of of copolymer int-butyl Experimental PDMS 1 PDMS 2 PDMS 3 a composition acrylate Example(g) (g) (g) (wt %) (g) PDMS 1-20 0.5716 — — 20 2.0796 PDMS 1-30 1.0808 —— 30 2.5375 PDMS 2-20 — 0.7022 — 20 2.8468 PDMS 2-30 — 0.9949 — 302.3370 PDMS 3-20 — — 0.5208 20 2.0905 PDMS 3-30 — — 0.9878 30 2.3090

Experimental Example PDMS 1, Experimental Example PDMS 2, andExperimental Example PDMS 3, were found to be well miscible with t-butylacrylate. The polymerization initiator was observed to be dissolved int-butyl acrylate.

2-2. Preparation of Composition for a Film According to First Monomer

A copolymer and a first monomer were mixed as in Table 2 below toprepare a composition. To the composition, an initiator was added.2,2-dimethoxy phenylacetophenone was used as an initiator, and about 0.5mol % of 2,2-dimethoxy-2-phenylacetophenone was added with respect tothe equivalent of a vinyl group in a mixture solution.

TABLE 2 Amount of first PDMS 2 PDMS 3 monomer used Sample name (g) (g)First monomer (g) PDMS-A — 0.3611 Methyl acrylate 1.4222 PDMS-B — 0.3812Ethyl acrylate 1.5497 PDMS-C — 0.3273 Methyl 1.3305 methacrylate PDMS-D— 0.3071 Vinyl acetate 1.2435 PDMS-E — 0.3021 Styrene 1.2016 PDMS-F —0.3457 Butyl acrylate 1.3610 PDMS-G 0.3228 — Hexyl acrylate 1.2968PDMS-H 0.3709 — Octyl acrylate 1.4883

3. Manufacture of Light Transmittance Control Film

Between a first substrate and a second substrate, a first spacer and asecond spacer were separately disposed in a horizontal direction. Glasssubstrates were used as the first and second substrates. A polyimideadhesive tapes with a thickness of about 100 μm were used as the firstspacer and the second spacer. A room was provided between the firstglass substrate and the second substrate, and between the first spacerand the second spacer. The composition was introduced into the roomusing capillary force. Ultraviolet light was irradiated for about 10minutes by using an ultraviolet lamp under nitrogen to manufacture aUV-cured film. The ultraviolet lamp was a Mercury UVH lamp with about 1KW. The UV intensity of the lamp applied on the composition layer wasmeasured to be 7.25, 8.85, 0.26, and 0.84 mW/cm² at 395˜445 (UVV),320˜390 (UVA), 280˜320 (UVB), and 250˜260 (UVC) nm, respectively. Then,the first and second substrates were dipped in distilled water for about24 hours, and the UV-cured film was removed from the first and secondsubstrates and vacuum dried at room temperature for about 2 hours.Accordingly, a light transmittance control film was obtained.

Experimental Example F 1-20, Experimental Example F 1-30, ExperimentalExample F 2-20, Experimental Example F 2-30, Experimental Example F3-20, and Experimental Example F 3-30 are films UV-cured from thecompositions of Experimental Example PDMS 1-20, Experimental ExamplePDMS 1-30, Experimental Example PDMS 2-20, Experimental Example PDMS2-30, Experimental Example PDMS 3-20, Experimental Example PDMS 3-30,respectively.

Hereinafter, FIG. 6 to FIG. 11 c will be explained with reference toFIG. 1 , FIG. 2 , and FIG. 3 .

FIG. 6 is a graph showing light transmittance of Experimental Example F1-20, Experimental Example F 1-30, Experimental Example F 2-20,Experimental Example F 2-30, Experimental Example F 3-20, andExperimental Example F 3-30 films in accordance with wavelength.

Referring to FIG. 6 , Experimental Example F 1-20, Experimental ExampleF 1-30, Experimental Example F 2-20, Experimental Example F 2-30,Experimental Example F 3-20, and Experimental Example F 3-30 films werefound to have high light transmittance in a visible region. Withincreasing the molar ratio of the first polymer, the light transmittanceof the light transmittance control film (1000) was increased.

Referring to FIG. 6 , if the molar ratio of the first polymer in thecomposition (10) for a light transmittance control film increases, thefirst monomer (100) may be reacted to the first polymer during apolymerization reaction process. In the polymerization reaction process,the polymerization between the first monomer (100) may be relativelydecreased. Accordingly, the compatibility of the matrix part (P2) withthe dispersed part (P1) may increase. The homopolymer from the firstmonomer (100) may be composed of the dispersed part (P1) in the lighttransmittance control film (1000). Due to the increase of thecompatibility of the matrix part (P2) with the dispersed part (P1), thediameter of the dispersed part (P1) may decrease. If the diameter of thedispersed part (P1) decreases, the light transmittance of the lighttransmittance control film (1000) may increase. If the weight percent ofthe first monomer (100) in the composition (10) for a lighttransmittance control film increases, the polymerization between thefirst monomer (100) during the polymerization reaction process may berelatively increased. Accordingly, the compatibility of the matrix part(P2) with the dispersed part (P1) may decrease. The homopolymer from thefirst monomer (100) may be composed of the dispersed part (P1) of thelight transmittance control film (1000). Due to the decrease of thecompatibility of the matrix part (P2) with the dispersed part (P1), thediameter of the dispersed part (P1) may increase. If the diameter of thedispersed part (P1) increases, the light transmittance of the lighttransmittance control film (1000) may decrease.

FIG. 7 a is a result showing light transmittance Experimental Example F3-20 film in accordance with tensile strain. e500, e600, and e700 arethe transmittance variation of Experimental Example F 3-20 film at awavelength of about 500 nm, about 600 nm, and about 700 nm,respectively. Table 3 shows the coefficient of determination (r²)calculated from the transmittance variation of e500, e600, and e700 inFIG. 7 a.

Referring to FIG. 7 a , with increasing tensile strain, the lighttransmittance of the light transmittance control film (1000) in avisible region may decrease. Referring to Table 3, the coefficient ofdetermination calculated from the transmittance variation of the lighttransmittance control film (1000) in accordance with tensile strain mayapproach 1. From this, it may be found that the light transmittance ofthe light transmittance control film (1000) linearly decreased inaccordance with the tensile strain. According to exemplary embodiments,the light transmittance of the light transmittance control film (1000)may be controlled by controlling the intensity of tensile force appliedto the light transmittance control film (1000) within the elastic regionof the light transmittance control film (1000).

TABLE 3 e500 e600 e700 Wavelength of light (nm) 500 nm 600 nm 700 nmCoefficient of 0.9932 0.9921 0.9924 determination

FIG. 7 b is an analysis result of the light transmittance ofExperimental Example F 2-20, Experimental Example F 3-20, andExperimental Example F 3-30 films in accordance with the wavelength oflight while tensile strain is applied to a light transmittance controlfilm. In this case, a tensile strain of about 0.2 was applied.

Referring to FIG. 7 b with FIG. 5 , under the same wavelength and thesame tensile strain conditions, light transmittance of ExperimentalExample F 3-30, Experimental Example F 3-20, and Experimental Example F2-20 films were increased in this order. As explained Table 4, the sizesof the dispersed part (P1) in the light transmittance control film(1000) of Experimental Example F 2-20, Experimental Example F 3-20, andExperimental Example F 3-30 films may increase in this order. If theapplied tensile force is constant, the volumes of voids (400) formedbetween the dispersed part (P1) and the matrix part (P2) may increasewith increasing the sizes of the dispersed part-(P1). The lighttransmittance change efficiency of the light transmittance control film(1000) may increase with increasing the diameters of the dispersed part(P1). According to exemplary embodiments, when tensile force is appliedto the light transmittance control film (1000), the light transmittancechange efficiency of the light transmittance control film may becontrolled by controlling the molar ratio of the first polymer or theweight percent of the first monomer (100) in the composition (10 in FIG.1 ) for a light transmittance control film.

FIG. 8 a is a scanning electron microscope (SEM) plain image ofExperimental Example F 2-20 film while a tensile strain of 0.2 isapplied to a light transmittance control film. FIG. 8 b is a SEM imageof Experimental Example F 2-20 film while a tensile strain of 0.4 isapplied to a light transmittance control film. FIG. 8 c is a SEM imageof Experimental Example F 2-20 film while a tensile strain of 0.8 isapplied to a light transmittance control film. Table 4 shows the resultsof Experimental Example F 2-20 film observed from the SEM images while atensile strain of 0.2, 0.4, or 0.8 was applied to the lighttransmittance control film.

TABLE 4 Applied tensile strain 0.2 0.4 0.8 Volume change of X X Xdispersed part (P1) Observed results of voids Voids are Voids thus Voidsthus formed between formed formed have formed have dispersed part (P1)and large volume very large matrix part (P2) volume.

Referring to FIG. 8 a , FIG. 8 b , FIG. 8 c , and Table 4 along withFIG. 5 , it was found that the volume of the voids (400) formed betweenthe dispersed part (P1) and the matrix part (P2) increased withincreasing applied tensile strain. In this case, the volume change ofthe dispersed part (P1) was rarely shown even though tensile force wasapplied. This result may be because the initial elastic coefficient ofthe dispersed part (P1) was large. The initial modulus of poly(t-butylacrylate) which was the practically dispersed part (P1), was measured atabout 1.14 GPa, which was greater 1000 times or more than that of acrosslinked PDMS (matrix part (P2)) which had generally about 1 MPa orless. The UV-cured film fabricated from the composition of Example 2-2did not show stress-whitening phenomenon according to the elongation bytensile force. This is because the initial modulus of the homopolymer ofwhich the dispersed part (P1) is composed is low and about 100 MPa orless. If the initial modulus difference between the dispersed part (P1)and the matrix part (P2) decreases, voids may not be formed between thedispersed part (P1) and the matrix part (P2), which does not showstress-whitening phenomenon. According to exemplary embodiments, thetransmittance of the light transmittance control film (1000) maydecrease due to the stress-whitening phenomenon of the lighttransmittance control film (1000). For example, the light transmittanceof the light transmittance control film (1000) may be controlled bycontrolling the intensity of tensile strain which is applied to thelight transmittance control film (1000).

Table 5 shows measured results of the initial modulus, the maximumtensile strength, the yield tensile strain, and the maximum tensilestrain of Experimental Example F 1-20, Experimental Example F 1-30,Experimental Example F 2-20, Experimental Example F 2-30, ExperimentalExample F 3-20, and Experimental Example F 3-30 films. In Table 5, s.d.in parenthesis means a standard deviation. The initial modulus, themaximum tensile strength, the yield tensile strain, and the maximumtensile strain of the experimental examples were measured by using TAInstrument RSA-G2.

TABLE 5 Maximum Yield Maximum Experimental Initial modulus tensilestrength tensile strain tensile strain Example (MPa) (s.d.) (MPa) (s.d.)(s.d.) (s.d.) F 1-20 15.67 (1.60) 3.49 (0.16) 0.10 (0.01) 1.02 (0.09) F1-30  2.31 (0.32) 3.04 (0.23) 0.22 (0.02) 2.23 (0.24) F 2-20 16.70(2.28) 9.03 (0.53)  0.17 (0.006) 1.29 (0.14) F 2-30  6.47 (1.74) 7.75(0.82) 0.26 (0.05) 2.60 (0.17) F 3-20 34.24 (5.18) 12.95 (1.82)  0.17(0.02) 1.06 (0.20) F 3-30  9.24 (0.68) 10.29 (0.27)  0.47 (0.07) 2.04(0.15)

Referring to Table 5, if the weight percent of the copolymer in thecomposition (10) for a light transmittance control film increases, theinitial modulus decreases, and the yield tensile strain and the maximumtensile strain increase. If the molar ratio of the first polymer in thecopolymer increases, the maximum tensile strength of the lighttransmittance control film (1000) may increase. The maximum tensilestrength of the light transmittance control film (1000) may increasewith increasing the amount of the reactive group in the copolymer.

The first polymer may have a reactive group. If the amount of thereactive group in the copolymer increases, in other words, if the molarratio of the first polymer in the copolymer increases, the amount andsize of the dispersed part (P1) in the light transmittance control film(1000) thus manufactured may decrease, and the amount of the graftedpolymer (110) with respect to the matrix part (P2) may increase.According to the amount of the dispersed part (P1) and the graftedpolymer (110), the physical properties of the light transmittancecontrol film (1000) may be changed. According to exemplary embodiments,by controlling the molar ratio of the first polymer in the composition(10) for a light transmittance control film, the initial modulus, themaximum tensile strength, the yield tensile strain, and the maximumtensile strain of the light transmittance control film (1000) may becontrolled.

FIG. 9 is a graph showing analysis results of differential scanningcalorimetry of Experimental Example F 1-20, Experimental Example F 1-30,Experimental Example F 2-20, Experimental Example F 2-30, ExperimentalExample F 3-20, and Experimental Example F 3-30 films. In FIG. 9 , theaxis of abscissa represents the temperature, and the axis of ordinaterelatively represents heat flow of the reaction. The differentialscanning calorimetry analysis was performed under a nitrogen flow ofabout 50 ml/min in a temperature range of about −100° C. to about 150°C. at a heating rate of 10° C./min by using a TA Instruments DSC Q20.

Referring to FIG. 9 , peaks were observed between about 45° C. and about50° C. in Experimental Example F 1-20, Experimental Example F 1-30,Experimental Example F 2-20, Experimental Example F 2-30, ExperimentalExample F 3-20, and Experimental Example F 3-30 films. The glasstransition temperature of the grafted polymer chain-(110) and thedispersed part (P1) (poly(t-butyl acrylate)) may be in this temperatureregion. Peaks in a region from about −55° C. and about −50° C. were alsoobserved in Experimental Example F 1-20, Experimental Example F 1-30,Experimental Example F 2-20, and Experimental Example F 2-30. Themelting temperature of the matrix part (P2) is in this temperatureregion. With increasing the amount of the dispersed part (P1) or theamount of the first polymer in the light transmittance control film(1000), the heat of fusion of the light transmittance control film(1000) was found to decrease. In Experimental Example 3-20 andExperimental Example 3-30 films, no peaks corresponding to the meltingpoint of the matrix part (P2) were observed at about −100° C. or more.It was found that Experimental Example F 1-20, Experimental Example F1-30, Experimental Example F 2-20, Experimental Example F 2-30,Experimental Example F 3-20, and Experimental Example F 3-30 films wereamorphous at room temperature (about 25° C.).

FIG. 10 a , FIG. 10 b , FIG. 10 c , and FIG. 10 d are transmissionelectron microscope (TEM) cross-sectional images of Experimental ExampleF 1-20, Experimental Example F 2-20, Experimental Example F 3-20, andExperimental Example F 3-30 films. JEM-ARM200F Cs-corrected scanningtransmission electron microscope was used for the TEM measurement.

Referring to FIG. 10 a , FIG. 10 b , FIG. 10 c , and FIG. 10 d ,dispersed part (P1) are densely distributed in a matrix part (P2).Referring to FIG. 10 a , an average size of the dispersed part (P1) in along axis direction was found to be about 300-500 nm or more. An averagesize of the dispersed part (P1) in a short axis direction was about 200nm or more. Referring to FIG. 10 b , an average size of the dispersedpart (P1) in a long axis direction was observed to be about 200 nm. Anaverage size of the dispersed part (P1) in a short axis direction wasabout 100 nm. Referring to FIG. 10 c , an average size of the dispersedpart (P1) in a long axis direction was observed to be about 100 nm toabout 150 nm. A size of the dispersed part (P1) in a short axisdirection was about 50 nm to about 100 nm. Referring to FIG. 10 d , anaverage size of the dispersed part (P1) in a long axis direction wasobserved to be about 100 nm. An average size of the dispersed part (P1)in a short axis direction was about 50 nm or less.

The vinyl group of the first polymer of the copolymer (200) in thecomposition (10) for a light transmittance control film may act as areactive group. The molar ratio of the first monomer (for example,t-butyl acrylate) to the reactive group in the copolymer (200) used forthe preparation of Experimental Example F 1-20, Experimental Example F2-20, Experimental Example F 3-20, and Experimental Example F 3-30 filmswere calculated as 83.0:1, 42.4:1, 20.5:1, and 12.0:1, respectively. Ifthe amount of the reactive group increases, the amount ratio of agrafted polymer (110) (for example, grafted poly(t-butyl acrylate)) inthe light transmittance control film (1000) may increase. Since thegrafted polymer chain (110) acts as a compatibilizing agent between thematrix part (P2) and the dispersed part (P1), the size of the dispersedpart (P1) may decrease. The dispersed part (P1) may have an ellipticalshape.

FIG. 11 a is a photo-image of Experimental Example F 3-20 film whiletensile force is not applied. FIG. 11 b is a photo-image of ExperimentalExample F 3-20 film during applying tensile force. FIG. 11 c is aphoto-image of Experimental Example F 3-20 film when tensile force isremoved after the application of the tensile force.

Referring to FIG. 11 a , a light transmittance control film (1000) whiletensile force is not applied, may be transparent.

Referring to FIG. 11 b , if tensile force is applied, the lighttransmittance of the light transmittance control film (1000) maydecrease. That is because stress-whitening phenomenon occurs as tensileforce is applied to the light transmittance control film (1000). Asexplained previously referring to FIG. 5 and Table 4, voids (400) may beformed between the dispersed part (P1) and the matrix part (P2), and thevoids (400) may be under vacuum or air may be supplied into the voids(400). The dispersed part (P1) and the matrix part (P2) may have a greatdifference of refractive index from vacuum or air. Due to the differenceof the refractive index, visible light may be scattered or reflected.Accordingly, the light transmittance of the light transmittance controlfilm (1000) may decrease. For example, the light transmittance controlfilm (1000) may become opaque. That is, the background under the lighttransmittance control film (1000) was not seen. Based on the lines drawnin the figures, tensile strain was about 0.15-0.2.

Referring to FIG. 11 c , if tensile force is removed, the lighttransmittance of the light transmittance control film (1000) mayincrease again. That is because the copolymer (200) has excellentelasticity recovery properties, and the matrix part (P2) returns tosubstantially the initial state as that before applying the externalforce. For example, the light transmittance control film (1000) maybecome transparent. The background under the light transmittance controlfilm (1000) was observed again.

The above-disclosed detailed description of the present invention is notintended to limit the present invention to disclosed exemplaryembodiments, but may be used in various combinations, changes andenvironments only if within the gist of the present invention. Attachedclaims should be interpreted to include other embodiments.

1. A light transmittance control film, comprising: a matrix partcomprising a copolymer and a polymer chain which is grafted to thecopolymer, wherein the copolymer comprises a first polymer derived froma second monomer and a second polymer derived from a third monomer; anda dispersed part comprising a polymer derived from a first monomer, thedispersed part being provided in the matrix part, wherein the polymerchain is derived from the first monomer, wherein voids are generatedbetween the dispersed part and the matrix part while an external forceis applied, and the voids disappear after the external force is removed.2. The light transmittance control film of claim 1, wherein first lighttransmittance is shown while the external force is applied, and secondlight transmittance which is greater than the first light transmittanceis shown after the external force is removed.
 3. The light transmittancecontrol film of claim 2, wherein the second light transmittance is about35% to about 95% in a visible region.
 4. The light transmittance controlfilm of claim 1, wherein an initial modulus of the dispersed part ishigher than an initial modulus of the matrix part.
 5. The lighttransmittance control film of claim 4, wherein the initial modulus ofthe dispersed part is about 100 to about 100,000 times more than theinitial modulus of the matrix part.
 6. The light transmittance controlfilm of claim 1, wherein a difference between a refractive index of thematrix part and a refractive index of the dispersed part is less thanabout 5%.
 7. The light transmittance control film of claim 1, whereinthe external force comprises tensile force.
 8. The light transmittancecontrol film of claim 1, wherein the first monomer is represented by thefollowing Formula 1:

in Formula 1, A1 and A2 are each independently a single bond, oxygen(O), —NH—, or sulfur (S), R1 is hydrogen, halogen, linear or branchedalkyl group of 1 to 8 carbon atoms, or halogen-substituted linear orbranched alkyl group of 1 to 8 carbon atoms, and R2, R3, and R4 are eachindependently hydrogen, halogen, or linear or branched alkyl group of 1to 5 carbon atoms.
 9. The light transmittance control film of claim 8,wherein the matrix part is represented by the following Formula 6A:

in Formula 6A, R11 is represented by the following Formula 2B, R12, R13,and R14 are each independently hydrogen, halogen, linear or branchedalkyl group of 1 to 5 carbon atoms, or substituted or unsubstitutedphenyl group of 6 to 13 carbon atoms, R15 is represented by thefollowing Formula 6B, and R16 is represented by the following Formula6C:

in Formula 2B, * means a bonded part of Formula 6A to Si, B is a singlebond, or linear or branched alkyl group of 1 to 5 carbon atoms,carbonyl, ester, acetate, amide, or —S—CO— group, and R21, R22, and R23are each independently hydrogen, halogen, or linear or branched alkylgroup of 1 to 5 carbon atoms:

in Formula 6B, * means a part bonded to Si in Formula 6A, A1 and A2 areeach independently a single bond, oxygen (O), —NH—, or sulfur (S), B isa single bond, linear or branched alkyl group of 1 to 5 carbon atoms,carbonyl, ester, acetate, amide, or —S—CO— group, R1 is hydrogen,halogen, linear or branched alkyl group of 1 to 8 carbon atoms, orhalogen-substituted linear or branched alkyl group of 1 to 8 carbonatoms, R2, R3, and R4 are each independently hydrogen, halogen, orlinear or branched alkyl group of 1 to 5 carbon atoms, R21, R22, and R23are each independently hydrogen, halogen, linear or branched alkyl groupof 1 to 5 carbon atoms, or substituted or unsubstituted phenyl group of6 to 13 carbon atoms, and m6 is an integer selected from 1 to 100:

in Formula 6C, * means a part bonded to Si in Formula 6A, A1 and A2 areeach independently a single bond, oxygen (O), —NH—, or sulfur (S), B isa single bond, linear or branched alkyl group of 1 to 5 carbon atoms,carbonyl, ester, acetate, amide, or —S—CO— group, R1 is hydrogen,halogen, linear or branched alkyl group of 1 to 8 carbon atoms, orhalogen-substituted linear or branched alkyl group of 1 to 8 carbonatoms, R2, R3, and R4 are each independently hydrogen, halogen, orlinear or branched alkyl group of 1 to 5 carbon atoms, R21, R22, and R23are each independently hydrogen, halogen, linear or branched alkyl groupof 1 to 5 carbon atoms, or substituted or unsubstituted phenyl group of6 to 13 carbon atoms, and m7 is an integer selected from 1 to
 100. 10.The light transmittance control film of claim 1, wherein the film istransparent and colorless before applying the external force.